If you are referring "simple" for the user interface then I find Yobit the most simple to use platform, you don't have anything to do there except to wait for a pump. When you see a pump get in. However, Yobit is not trusted.

The second platform I find simple enough is Poloniex.

Binance & Bitmex which I prefer the most for trading is because they offer an advanced trading platform and of course they have volume.
If you stick with these exchanges for a few days then you will know how to play with it.